Electrolyte for use in electrometallurgy.



UNITED STATES PATENT OFFICE.

1\TICOL.AS HENRI MARIE DEKKER, OF IEARIS, FRANCE.

ELECTROLYTE FOR USE IN ELECTROMETALLURGY.

No Drawing.

To all whom it may concern:

Be it known that I, NIooLAs HENRI MARIE DEKKER, subject of the Kingdomof the Netherlands, residing at 29 Rue de la Sourdire, Paris, France,have invented new and useful Improvements in or Relating to Electrolytesfor Use in Electrometallurgy, of which the following is a specification.

In electrolytic operations secondary reactions are always found due tothe decomposition of the water which in its turn is due to the presenceof free acid in the bath, which acid favors the formation of hydrogenand oxygen which produce basic salts, oxids, etc., which unfavorablyaffect the operation. Of all the usual metals, only one can be treatedin a practical manner at the present time, namely copper which isgenerally produced in that way, but that production relates only to therefining of the mattes, for it has not hitherto been possible to obtaincopper by exhausting a complex electrolyte. The greatest difficulty atpresent met with in obtaining good electrolytic deposits, 'is thereforedue to water di-.

. lutions without which no electrolysis have hitherto been undertakenand when it is desired to obtain by electrolysis a metal, by refining,the operation is always carried out with baths obtained by dissolving inwater a salt of the metal to be obtained to which, are added one or moreother salts of different metals generally of alkaline metals. In orderto avoid that disadvantage, ithas been suggested to use hygroscopicsalts, but without success, because that method always leads tosecondary reactions due to the use of these salts or to hydrogen oroxygen or to both these gases produced by the decomposition of the waterby the free acid. It has thus been found that hydrids, oxids or basicsalts of zinc are formed during electrolysis of salts of zinc. In thesame way, it has been found that basic salts or oxid of iron are formedin the electrolysis of an iron salt.

In order to avoid the disadvantages due to the decomposition of water,that is to say, to the presence in the baths, of oxygen and hydrogen dueto the presence of free acid, it has been suggested to use sulfurousgas, chlo in, air deprived of its oxygen, etc. It

* has een even suggested to add to the baths oxi izing or reducingsubstances, according to the result to be obtained, but always withoutappreciable success, all these at- Specification of Letters Patent.

Application filed August 17, 1912.

Patented Oct; 13, 1914. Serial No. 715,593.

tempts having failed owing to the formation of hydrogen or oxygen orboth gases, according to individual cases.

The present invention has for its object an electrolytic process forrefining metals whichprocess is exempt from the drawbacks hereinbeforementioned, and which is suitable for obtaining all usual metals such asiron, copper, zinc aluminum, manganese, titanium, bromium, and the like.

The following are examples of the salts which may be used in carryingout this process:

'ZnSO,H O-. It is therefore the water constitutin thecrystal or water ofcrystallization. 1% is not free, and the part played by it, cannotbecompared to that of the water that would be used for dissolving thismolecule, and called water of solution.

According to the present invention, the refining of a metal is producedby electrolyzing a bath containing a salt of this metal and notcomprising any water but the water gf I(irystalliz'ation of the saltsforming the In order to prepare the electrolytic bath, a crystallizedsalt of the metal to berefined is subjected to the action of heat,'insuch a manner as this salt is melted in 1ts water of crystallization, orit will be dissolved in an alkaline or earthlike sulfate, melted bymeans of heat in its water of crystallization.

For the purpose of liberating the baths of water of solution or freewater, in the first series of experiments water of crystallization ofsulfate of magnesia MgSOJILO has previously been used for the purpose ofdissolving the sulfate of the metal to be refined,

refining metals. This method may be replaced by a simpler one givingmuch better results: When any salt is dissolved in its water ofcrystallization, a portion or the whole of this water evaporates, andthe salt passes-into the anhydrous state, or, if the temperature is toohigh, it becomes decomposed. If, however, during the dissolving of thissalt in its water of crystallization, a given quantity of water ofsolution is added for each salt in question, the bath always remainsliquid and atter the subsequent operation will contain, at the moment ofits use, only the quantity of water corresponding to that contained inthe weight of the crystallized salt used. In fact, if the bath isallowed to cool, the salt will crystallize in a solid mass withoutmotherliquor. A bath thus prepared, remains liquid provided that itstemperature is kept up at a slightly higher level than that at which itwould become crystallized by cooling. It is thus possible to prepare theelectrolytic bath by heating a salt of the metal considered containingno water of dissolution. From time to time, a little water is addedmerely to compensate for the small quantity of water of crystallizationwhich evaporates.

When an electrolytic operation is efiected with a bath prepared, thegeneration of oxygen and hydrogen is done away with, for in the bath inquestion, the water does not seem to be exposed to the decomposingaction of the current. It appears to have for its function merely tokeep up the constitution of the molecules of the molten salt, and thewhole reaction takes place as if one had to deal with a fused salt.

During the refining operation, as soon as the metal of the electrolyteis separated from the acid in order to settle on the cathode, the said.acid becomes concentrated on the anode and attacks it, in order toreconstitute the electrolyte. Consequently, the bath always retains itsacid saturated with metal, that is to say, it always has the samerichness or proportion of salt. The bath will therefore always remainnot only con- 'centrated, but saturated. Owing to that fact, nodecomposition of water takes place. Moreover, the water of this bath isalways in combination, and never free. If it is desired to refineaccording to the invention a piece of cast iron, this piece will betaken as anode and the electrolytic bath will be (detained by melting inits water of crystallization the molecule FeSOJH O. During theelectrolysis, the iron settles on the cathode, while the group SO, innascent state attacks the cast iron for producing FeSO, which, with the7H,O,- reconstitutes the molecule FSOJH O of the bath.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is 1. An electrolytic process for refining metalsconsisting in placing an anode and a cathode in an electrolyteconsisting of a salt oi the metal to be refined but no water except thewater of crystallization of the salts in presence and passing a currentfrom i the anode through the electrolyte to the cathode.

2. An electrolytic process for refining metals consisting in placing ananode and a cathode in an electrolyte consisting of a salt of the metalto be refined but no water except the water of crystallization of thesalts in presence, the electrolytic bath being prepared by melting asalt of the metal to he refined, and adding only the amount of waterwhich is necessary for replacing the water of crystallization evaporatedin the bath, owing to the heating and passing an electric currentthrough the anode, electrolyte and cathode.

3. An electrolytic process for refining metals consisting in placing ananode and cathode in a. bath containing a salt of the metal to berefined but no water except the water of crystallization of the salts inpresence, the electrolytic bath being prepared by solving a salt of themetal to be refined in an alkaline or earthlike sulfate melted by meansof heat in its water crystallization and passing a current through saidanode, bath and cathode.

In testimony whereof I afiix my signature in presence of two witnesses.

NICOLAS HENRI MARIE DEKKER. Witnesses H. C. COXE, J. BEE.

